Electromagnetic or permanent-magnetic rail brake

ABSTRACT

A magnetic rail brake, particularly an eddy current brake for rail vehicles, has at least one exciter coil which comprises a coil around a pole core as well as a device for holding the coil and/or for the protection against outside environmental influences. The pole core and/or protection device are composed of individual components which are at least largely electrically insulated with respect to one another.

BACKGROUND AND SUMMARY OF THE INVENTION

The invention relates generally to an electromagnetic orpermanent-magnetic rail brake, and more particularly to a linear eddycurrent brake for rail vehicles.

In modern wheel/rail engineering, there is demand for brake technologieswhich have a brake force that is as much as possible independent of thecoefficient of adhesion between the wheel and the rail. Linear eddycurrent brakes naturally meet this requirement in an ideal fashionbecause, as non-contact service brakes, they are absolutely independentof the coefficient of adhesion.

A short introduction into the technology of the eddy current brakes forrail vehicles--whose function is based on the law of induction--isfound, for example, in the book by Saumweber, et al. "AET--Archiv furEisenbahntechnik (Archive for Railway Technology)"--Hestra Publishers,Volume 43, Chapter 2.5.2. Eddy current brakes consist of an iron yokewith several pole cores. Electric coils magnetically excite the brakesuch that magnetic north and south poles are generated in an alternatingmanner. When the excited eddy current brake is moved along therail--that is, during a braking--, electromagnetic fields and eddycurrents are generated as a result of the changes of the time rate offlow. The secondary magnetic field caused by the eddy currents isopposed to the magnetic field of the brake. The resulting horizontalforce component which acts opposite to the travelling direction is thebrake force.

Despite the important advantage of this brake of having no contact withrespect to rail, the practical use of eddy current brakes in large partis delayed by the fact that the compatibility of the brake with theexisting operating equipment of various railroad operators can still beoptimized.

A problem of the above-mentioned type, which results in seriousdifficulties during the practical application, is the interferinginfluence of the eddy current brakes on electromagnetic axle countersand/or similar sensing devices.

This problem is described in detail in European Patent Document EP 0 309651. A large portion of the currently existing track sections of thevaried railroad operators have rails which are provided with axlecounting sensors laterally below the rail surface. Generally,electromagnetic sensors are used for the axle counting. That is, atransmitter sends out an electromagnetic alternating field (of afrequency of 5 to typically 43 kHz) and, when a metal wheel travels overa sensor arranged on the opposite side of the rail, the sensor registerschanges of the electric field, which are caused by the metal wheel, withrespect to the amplitude and the direction as counting pulses. A trainpassing through the sensor arrangements triggers a counting pulse in thesensors by each axle or wheel passing there through. If, during a passthrough locally mutually separate axle counters, different countingresults are registered, the track section is blocked for the followingtrain.

Since, during a braking, eddy current brakes are lowered from a highposition into a low position just above the rail, they may also triggercounting pulses in the axle counting sensors during the braking.However, they trigger counting pulses only in their low position (thus,during the braking) but not in their high position. Eddy current brakesmay therefore falsify the result of an axle count and stop a train forno reason.

For solving this problem, European Patent Document EP 0 309 651 A2suggests that guiding plates made of a ferromagnetic material be mountedon the outside in the area of the lower longitudinal edges of each coilof the brake magnet. These guiding plates each extend along the lowercorner edges of the exciter coil. Although the suggested solution easesthe problem, faulty signals cannot be excluded to an extent required fora controlled train operation.

From Austrian Patent Document 317 290, corresponding to U.S. Pat. No.3,805,927, an electromagnetic rail brake is known in which a rod made ofa ferromagnetic material extends along the length of the electromagneticrail brake to reduce disturbing influences. This solution also does notmeet the requirements of a high-speed traffic of eliminatingdisturbances from the rail operation.

The invention is based on the problem of providing an electromagnetic orpermanent-magnetic rail brake--particularly an eddy current brake--forrail vehicles which does not interfere with sensing devices, such asaxle counters, during braking operations.

The invention implements particularly an eddy current brake for railvehicles having at least one exciter coil which has a coil around a polecore and also has a device for holding the coil and/or for theprotection against outside environmental influences. The pole coreand/or the protection device is composed of individual components whichare at least largely electrically insulated with respect to one another.

The division into separate individual components interrupts thetransmission of a transmitted signal from a transmitter on one side ofthe rail to a receiver on the other side of the rail. Thus, virtually nomore interfering signals occur and the use of the eddy current brakebecomes possible in a large portion of the existing track systems. Thisbasically constructively simple measure effectively prevents interferingsignals. The invention therefore provides a decisive step in thepenetration of the market by means of the technically advantageous eddycurrent brake technology.

A large number of the axle counters, which are currently used inpractices are designed such that a metal wheel passing though the sensorin the receiver section produces a clearly recordable voltage change;for example, in one embodiment of the sensor, a voltage increase. Thiseffect is prevented by the invention. In this variant, a weakening ofthe signal may even take place by the brake according to the invention.Counting pulses are no longer triggered.

According to another embodiment of the invention, the protection deviceis designed as a multipart metal housing, in which case the individualmetal sections are insulated with respect to one another in the mountedposition of the brake in which the longitudinal axis of the brake isaligned essentially along the longitudinal axis of the rail.Correspondingly, it is advantageous for the pole core to have at leasttwo metal plates which are essentially insulated with respect to oneanother in the mounted position of the brake. Because of the skineffect, the wave transmission takes place essentially on the surface ofthe metal components. The division into individual layers effectivelyinterrupts this transmission.

According to another embodiment of the invention, at least one of themetal plates is ferromagnetic. Steel can be selected for reaching goodelectric transmission characteristics. In this case, the metal platesare arranged in a plane perpendicular to the longitudinal axis of therail.

In another embodiment, steel plates of the pole core are separated fromone another by transformer plates. For example, five steel plates andfour transformer plates are used. This embodiment achieves very goodresults with respect to the freedom from disturbances of axle counterswithout high demands constructively on the manufacturing of the polecore that, for reasons of cost, an implementation of the product wouldbe made more difficult.

A metal housing is generally used for protecting the coils. According tothe invention, it was found to be particularly advantageous for themetal housing to have lateral surfaces which are open transversely tothe longitudinal axis of the brake. The partially open lateral surfacesalso have an advantageous effect on the field distribution(short-circuit effect) and promote the effect of the laminated core. Infurther embodiments of the invention, at least one exciter coil isarranged in a housing made of glass fiber reinforced plastic and isfastened by a U-shaped carrying device on a brake anchor plate; and/orthe metal plates are screwed to one another and/or are glued to oneanother, and are therefore mechanically connected with one another in anon-conductive manner.

By the invention, an eddy current brake (or a rail vehicle with such abrake) can be implemented in an advantageous manner which meets therequirements with respect to the freedom from disturbances of mostdifferent high-speed railway lines, such as the ICE-train and theTGV-train.

In the following, the invention will be described in detail withreference to the drawing by means of embodiments, in which caseadditional advantages and possibilities of the invention also becomeclear.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a first embodiment of an eddy current brakeaccording to the invention;

FIG. 2 is a sectional view along Line A-A' of the embodiment from FIG.1;

FIG. 3 is a top view of a schematically illustrated pole coreconstructed according to the invention in a further embodiment of theinvention;

FIG. 4 is a partially cut lateral view of the pole core from FIG. 3;

FIG. 5 is a partially cut lateral view of another embodiment of anexciter coil according to the invention;

FIG. 6 is a top view of the exciter coil of FIG. 5.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

First the embodiment of FIG. 1 shows an eddy current brake 1 which canbe fastened to a pivoted bogie (which is not shown). During a brakingoperation of the train, the eddy current brake is held at a shortdistance in parallel to a rail 3. It has a brake anchor plate 3 on whichexciter coils 4 are arranged and which can be magnetized in analternating manner in a north/south sequence. The totality of theexciter coils 4 together with the anchor plate 3 are called the "brakemagnet".

FIG. 2 illustrates the construction and the mounted position of one ofthe exciter coils 4 of FIG. 1. The sectional view illustrates a metalcore 5 around which coil windings 6 are wound. In turn, the metal core 5has several individual metal plates 5a, 5b, etc. electrically insulatedfrom each other as in a laminated core. The metal core 5 is arranged onthe anchor plate 3 such that the individual metal plates 5a, 5b aresituated on the extension of the rail axis X and in the plane or inparallel to the plane defined by the rails axes X and Y. Laterally ofthe rail 2, a sensing device 7 is schematically shown which has atransmitter part 7a and a receiver part 7b.

FIGS. 3 and 4 show an embodiment of a coil core 5 of an eddy currentbrake according to the invention which, because of a bundling ofindividual metal plates 5a-5i, has particularly good electromagnetictransmission characteristics; that is, they avoid interfering signals inthe axle counters 7. The metal plates 5a, 5c, 5e, 5g, 5i of the polecore 5 are designed as steel plates and the metal layers 5b, 5d, 5f, 5hare designed as transformer plates--that is, as plates with aferromagnetic characteristic; and the plates 5b, 5d, 5f, 5h may also beinsulators. The center steel plate 5e is particularly strong andprovides stability to the pole core. A threaded bore 8 is used forfastening the pole core to the anchor plate 3 by a (not shown) stud. An(optionally multipart) base plate 9 carries the coil 6 (see FIG. 5 and6).

FIGS. 5 and 6 illustrate the mounted position of the exciter coil 4arranged in a housing (or box) 10 (protection device) made of a glassfiber reinforced plastic (GFK). The layered or laminated construction ofthe coil core 5 of the type of FIGS. 3 and 4 is easily recognizable. Thecoil windings 6 of the exciter coil 4 which surround the coil core 5 areschematically outlined. The plastic housing 10 encloses the exciter coil4 on all sides. Connections 11a and 11b are used for supplying electricenergy.

If a metallic protection device is used instead of the plastic housing10, it is advantageous to laterally open this metallic protection devicetransversely with respect to the rail or to design it according to thetype of FIG. 2 as double yokes 10' which border the exciter coil 4 alongthe rail transversely with respect to the rail but physically separatedfrom another and are therefore electrically insulated with respect toone another. Instead of a housing, such a yoke-type double bordering 10'is provided in FIG. 1 as the protection device for protecting againstoutside environmental influences, such as stoning, and for fastening theexciter coil 4. The yoke bordering 10' is open on its bottom side, thus,in the mounted position, toward the rail as well as transversely to therail (thus in an area in which the exciter coils 4 are already disposedclosely side-by-side). The yoke is a U-shaped carrying device.

Although the present invention has been described and illustrated indetail, it is to be clearly understood that the same is by way ofillustration and example only, and is not to be taken by way oflimitation. The principle is applicable to electro-magnetic andpermanent magnetic brake structures. The spirit and scope of the presentinvention are to be limited only by the terms of the appended claims.

We claim:
 1. A magnetic rail brake for a rail vehicle comprising:atleast one exciter coil which has a coil around a core; the coreincluding at least two individual components each having a longitudinalaxis parallel to a longitudinal axis of a rail; and the individualcomponents being separated from each other transverse to thelongitudinal axis of the rail and being electrically insulated withrespect to each other.
 2. A brake according to claim 1, including amultipart metal housing, individual metal sections of the housing beingelectrically insulated with respect to one another in a mounted positionof the brake wherein a longitudinal axis of the brake is essentiallyaligned along the longitudinal axis of a rail.
 3. A brake according toclaim 1 wherin the core has at least two metal plates which areessentially electrically insulated with respect to one another inmounted position of the brake.
 4. A brake according to claim 3, whereinat least one of the metal plates is ferromagnetic.
 5. A brake accordingto claim 1, wherein the core includes steel plates which areadditionally separated from one another by transformer plates.
 6. Abrake according to claim 1, including a metal housing having lateralsurfaces which are open transversely to a longitudinal axis of the brakewhich is essentially aligned with the longitudinal axis of a rail.
 7. Abrake according to claim 1, including a plastic housing.
 8. A brakeaccording to claim 1, a U-shaped carrying device fastening the at leastone exciter coil to a brake anchor plate.
 9. A brake according to claim1, wherein the core includes metal plates mechanically connected withone another in a non-conductive manner.
 10. A rail vehicle for travelingon railway lines whose rails are provided with magnetic sensing devices,particularly axle counters, including a magnetic rail brake, accordingto claim 1, which is also adapted to be positioned within the field ofthe magnetic sensing device.
 11. A brake according to claim 1, includingan anchor plate to mount the exciter coil with the core's longitudinalaxis along the longitudinal axis of the rail.
 12. A brake according toclaim 1, including a plurality of exciter coils spaced along thelongitudinal axis of the rail and having alternating polarity.